Connecticut College, New London, Connecticut usa general Physics Institute, Russian Academy of Sciences, Moscow, Russia
Download 1.65 Mb.
|
C1.CO2 DETECTION AROUND 2.05µm WITH A GaSb-BASED Quantum well LASER V. Zeninari, B. Parvitte Groupe de Spectrométrie Moléculaire et Atmosphérique (GSMA UMR CNRS 6089) Université Reims Champagne-Ardenne, BP 1039, 51687 Reims cedex 02, France. A Vicet, A Perona, P Grech and A. N. Baranov. Centre d’Electronique et de Microoptoélectronique de Montpellier (CEM2 UMR CNRS 5507) Université Montpellier II, 34095 Montpellier cedex 05, France. E-mail : a.vicet@univ-montp2.fr. Tel : 33 4 67 14 34 71 G. Durry Institut Pierre-Simon-Laplace, Service d’Aéronomie, CNRS BP3, 91371 Verrières-le-Buisson cedex, France. Continuous wave (cw) quantum well lasers have been fabricated at the CEM2 (Montpellier, France). The devices are based on a type I GaInAsSb/GaAlAsSb/GaSb multiple quantum well structure grown on n-GaSb substrates by molecular beam epitaxy (MBE). T  he active zone of the structure is made of three 10-nm-thick compressively strained GaInAsSb quantum wells between 30-nm-thick GaAlAsSb barriers. The 1.5-µm-thick optical confinement layers are made of Ga0.1Al0.9AsSb lattice matched with GaSb. The wafer was processed into 10 µm ridge waveguides providing single spatial mode emission and cleaved to 750-µm-long devices. The devices were then mounted on a Peltier cell for temperature stabilization and placed into a housing filled with dry nitrogen. The laser emission is centered near 2.05 µm at room temperature. Single frequency regime (fig. 1) can be obtained for these Fabry-Perot devices in a wide range of driving currents and temperatures without a grating or additional technological process. The emission line can be tuned by current with a rate of about 1.25 GHz/mA.
The laser diode has been tested on a laboratory spectrometer (GSMA, Reims, France). Some spectroscopic parameters (line strength and self-broadening coefficient) were determined for a line of the (2 00 1) (0 0 0) band. These parameters have been compared with other experimental results and available databases. This laser has also been tested on the laboratory version of the JETDLAG spectrometer developped by the Service d’Aéronomie of Verrières le Buisson (France). We demonstrate with this laser line the possibility to detect CO2 at ground level. C2.MOBILE METHANE SENSOR BASED ON 1.65 um DIODE LASER: RESULTS OF FIELD TESTS A.G.Berezin, O.V.Ershov, A.I.Nadezhdinskii, Yu.P.Shapovalov Natural Sciences Center of A.M.Prokhorov General Physics Institute of Russian Academy of Sciences 119991 GSP-1 Vavilova st. 38, Moscow, Russia The car-borne automated high sensitive methane detector was developed on a base of laboratory prototype [1] for measurements of methane concentrations during car movement. The device was tested in laboratory and field conditions. The measurements were performed with non-cryogenic-cooled near-infrared tunable diode laser operating at 1.65 um. The device incorporated multipass optical cell with optical path length 90 m at base length of 0.5 m. The main destination of the detector is the monitoring of methane content in the ambient air in order to find the gas leaks. Limit sensitivity (std) was found to be 0.1 ppm at 0.4 s. The detection technique based on registration of separate methane absorption line allowed reaching high selectivity of the detector with respect to other gases. The results of field tests on the streets and near gas-filling stations (methane) in Moscow are discussed. The detector could be rather easily adjusted for detection of other simple molecules such as CO, CO2, HF, NO2, H2O and others by change of the diode laser and corrections in software. [1] Nadezhdinskii A., Berezin A., Chernin S., Ershov O., Kutnyak V. Spectrochimica Acta Part A, 55, 2083 (1999). C3.Fast and Precise Frequency Tuning of Diode Lasers using a Quadrature Interferometer Th. Müller-Wirts1, K.-M. Knaak1, A. Deninger2 and W. Kaenders2 1TEM Messtechnik GmbH, Großer Hillen 38, 30559 Hannover, Germany 2TOPTICA Photonics AG, Fraunhoferstraße 14, 82152 Martinsried, Germany Uniting frequency stabilization and fast detuning of external-cavity diode lasers is a challenging task. Limitations arise due to temperature induced drift, non-linearity and hysteresis of mechanical components and actuators. Frequency stabilization commonly relies either on an absolute frequency reference, such as an atomic transition, or a relative standard, e.g. a Fabry-Perot interferometer. However, since atomic resonances are only available at a few distinct frequencies, and high finesse interferometers only permit frequency stabilization to the regularly spaced transmission peaks, both methods do not lend themselves to stabilization of a laser to an arbitrary frequency with high precision. We present a novel quadrature interferometer, designed as add-on for tunable lasers, which allows for performing fast and linear frequency scans. Any non-linearity of mechanics and piezo actuators is automatically compensated for. In addition, the interferometer provides a continuous relative frequency reference for an arbitrary tuning range. The concept is based on a measurement of the actual laser frequency using a temperature-controlled solid state etalon. Two probe beams strike the etalon under different angles, yielding interference signals with a relative phase of 90°. The signals are combined to provide a quadrature signal. The laser frequency corresponds to the phase of the quadrature signal, which can be precisely controlled. The module is well suited to a wide wavelength range (380 nm to 1100 nm already in the standard version, can be extended into the UV or IR by adapting the utilized photodetectors). The digital control is based on a 32-bit microprocessor. The thickness of the etalon determines resolution and final stability of the laser frequency, which is typically 400 times better than the selected Free Spectral Range (standard FSR is 17 GHz). Combining the quadrature interferometer and TOPTICA’s diode laser DL 100, a frequency stability of 5108 (20 MHz @ 850 nm) has been achieved. The digital frequency control also permits rapid frequency stepping: The laser frequency can be shifted in any desired manner and by an arbitrary amount without sacrificing accuracy for tuning speed. The quadrature interferometer is a versatile tool for applications involving laser monitoring, wavelength scanning or stepping, as well as wavelength locking. It provides a means to perform surveillance of wavelength drift, optimization of laser tuning parameters, monitoring of mode properties and stabilization (“locking”) of a laser to an arbitrary frequency. In addition, the laser is rendered insensitive to mechanical vibrations. Applications include accurate and linear frequency scanning for spectroscopy, laser cooling, plasma monitoring, LIDAR seeding, laser on- and off-line monitoring and examination of optical components using phase-shifting interferometry. C4.Compact and light-weight open-path-Herriott-cell for simultaneous In-situ-Detection of H2O and CH4 onboard of stratospheric balloon platforms C. Giesemann, T. Fernholz, H. Teichert, J. Wolfrum, V. Ebert Physikalisch-Chemisches Institut, University Heidelberg, INF 253, D-69120 Heidelberg contact: volker.ebert@pci.uni-heidelberg.de fax: 49-6221-545050 The depletion of stratospheric ozone is closely connected to the water vapor budget in the stratosphere, which is dominated by the entry of tropospheric water and the photolysis induced oxidation of CH4 in the stratosphere. In order to make up the balance of the stratospheric water budget and to better understand the underlying transport processes, it is necessary to obtain frequent and simultaneous in situ determination of vertical concentration profiles of both contributing species, up to heights of 30 to 40 km. This task can only be solved by lightweight, compact and nevertheless highly sensitive CH4-H2O in situ sensors. Up to now the available techniques relied on retrieving gas samples for analysis, making them very susceptible to systematic errors caused by adsorption effects. Theses devices are also heavy and consequently require higher financial costs so that they are only used sparingly. To address improved CH4-H2O detection, on of the most compact and lightweight dual-species diode laser absorption spectrometers for use aboard stratospheric balloon platforms was developed in cooperation with the Institutes of Environmental Physics in Bremen and Heidelberg1. This system is designed to simultaneously detect H2O at the 2n1 and CH4 at the 2n3 vibrational band. The core of this new instrument is a new compact, ultra-light-weight, multi-species open-path Herriott-cell, which allows the use of different path lengths for the two species (H2O 36m, CH4 76m). A base length of 55cm and an extremely compact dual-species optical head, which allowed to confine the overall size of the complete optical setup to 75cm by 25cm. The use of specifically designed opto-mechanical components constricted the overall weight of the complete optics (including lasers, detectors, etc.) to 6.6kg and the total weight of the instrument to 20kg including batteries. The spectrometer operation was validated during two stratospheric flights with maximum heights of up to 35 km. Despite temperature variations of more than 100K and a high number of reflections (136 in case of the methane absorption path), the system showed excellent mechanical stability. This was in large part due to a new passive thermal compensation system that was used to compensate even the thermal expansion of the invar rods that separate the two main mirrors. The expansion movements of the invar rods were reduced by nearly an order of magnitude. The distance between the mirrors could be constrained to less than 20µm over the full temperature range. During the first two flights pressure dependent detectivities of 150-500ppb for H2O and 50-600ppb for CH4 were achieved. The low weight and compactness of this new instrument therefore constitutes a significant improvement over current instrumentation and should allow a much more frequent determination of the H2O/CH4 profiles by flying this instrument either alone on much smaller and therefore cheaper balloons or piggy-back on board larger instruments. Directory: 2003 2003 -> Tr-41. 4-03-05-024 Telecommunications 2003 -> Review of some tsunamis in canada 2003 -> The skill of multi-model seasonal forecasts of the wintertime North Atlantic Oscillation 2003 -> 2930 Kerry Forest Parkway 2003 -> Canadian Interuniversity Sport (cis) Athletes of the Week 2003 -> Senior Airman Jason Plite Hometown 2003 -> Technical announcements: My apologies for the comparison pages; they were 2003 -> Pool Play Round 1 9: 20: 00 am 2003 -> 2004 Division II men's Golf Championships Final Round Results deland, fla 2003 -> Go Figure Edited by Kostya Kennedy and Mark Bechtel 645 Passing yards, an ncaa division II record, by University of Indianapolis quarterback Matt Kohn, in a 59-52 victory over Michigan Tech Download 1.65 Mb. Share with your friends:
|